In 3GPP (3rd Generation Partnership Project), a W-CDMA system is standardized as the third generation cellular mobile communication system, and service thereof has been started sequentially. In addition, HSDPA having a further improved communication speed is also standardized, and service thereof has been started.
Meanwhile, Evolved Universal Terrestrial Radio Access (hereinafter referred to as “EUTRA”) has being standardized in 3GPP. As a downlink communication system of EUTRA, an OFDM (Orthogonal Frequency Division Multiplexing) system has been employed that has resistance to multipath interference and is suitable for high-speed transmission.
In addition, as an uplink communication system of EUTRA, has been employed a DFT (Discrete Fourier Transform)-spread OFDM system of SC-FDMA (Single Carrier-Frequency Division Multiple Access) that can reduce a PAPR (Peak to Average Power Ratio) of a transmission signal in consideration of cost and power consumption of mobile station apparatuses (MS1 to MS3).
As a downlink of EUTRA, the OFDM (Orthogonal Frequency Division Multiplexing) system has been proposed. In addition, as an uplink of EUTRA, a single-carrier communication system of the DFT (Discrete Fourier Transform)-spread OFDM system has been proposed.
The downlink of EUTRA is comprised of: a DPiCH (Downlink Pilot Channel); a DSCH (Downlink Synchronization Channel); a PDSCH (Physical Downlink Shared Channel); a PDCCH (Physical Downlink Control Channel); and a CCPCH (Common Control Physical Channel).
As shown in FIG. 16, the uplink of EUTRA is comprised of: a UPiCH (Uplink Pilot Channel); a RACH (Random Access Channel); a PUSCH (Physical Uplink Shared Channel); and a PUCCH (Physical Uplink Control Channel) (for example, refer to Non-Patent Document 1).
A configuration example of the uplink is shown in FIG. 17. One block is comprised of twelve subcarriers and seven OFDM symbols. Additionally, two blocks are used to be comprised in one resource block. The physical uplink shared channel PUSCH and the physical uplink control channel PUCCH are allocated to each mobile station apparatus by setting one resource block as a minimum unit. As for the random access channel RACH, one random access channel is prepared in one subframe and responds to access from a number of mobile station apparatuses. The above-described configuration of the random access channel RACH is informed to a mobile station apparatus as notifying information by a base station apparatus BS. The random access channel is arranged regularly, and the random access channel RACH, a region of the physical uplink shared channel PUSCH, and a region of the physical uplink control channel PUCCH are separated from each other as shown in FIG. 17. It is to be noted that the random access channel RACH is comprised of six resource blocks (for example, refer to Non-Patent Document 1).
The physical uplink shared channel PUSCH is utilized for data transmission of the mobile station apparatus. The physical uplink control channel PUCCH is used for transmission of a response (Ack/Nack) to the physical downlink shared channel PDSCH, a downlink CQI (Channel Quality Indicator), and an uplink wireless resource (physical uplink shared channel PUSCH) request (scheduling request). Positions of the physical uplink control channel PUCCH for transmitting the downlink CQI and the scheduling request are previously allocated to the mobile station apparatus establishing uplink synchronization with the base station apparatus, and the response to the physical downlink shared channel PDSCH is informed using scheduling information of the physical downlink shared channel PDSCH.
An object to use the random access channel is to synchronize between the mobile station apparatus and the base station apparatus in the uplink (adjust uplink transmission timing from the mobile station apparatus to the base station apparatus). A random access procedure includes two kinds of random access, i.e., Contention based Random Access as shown in FIG. 18 and Non-contention based Random Access as shown in FIG. 19. The Contention based Random Access is the random access in which collision may occur between the mobile station apparatuses, the Access being the usually performed one. The Non-contention based Random Access is the random access in which collision does not occur between the mobile station apparatuses, and which is performed by an instruction from the base station apparatus in a special case of handover etc. in order to quickly synchronize between the mobile station apparatus and the base station apparatus (for example, refer to Non-Patent Document 2).
When the mobile station apparatus accesses the random access channel RACH, it transmits only a random preamble. The random access preamble is comprised of a preamble portion and a CP (Cyclic prefix) portion. A CAZAC (Constant Amplitude Zero Auto-Correlation Zone Code) sequence, which is a signal pattern indicating information, is used for the preamble portion, and 6-bit information is represented by preparing sixty-four types of sequences.
A Contention based Random Access procedure will be described simply. First, a mobile station apparatus transmits a random access preamble to a base station apparatus (message 1: M1). Subsequently, the base station apparatus having received the random access preamble transmits a response to the random access preamble (random access response) to the mobile station apparatus (Message 2: M2). The mobile station apparatus transmits a message of upper layers (Layer2/Layer3) based on scheduling information included in the random access response (Message 3: M3). The base station apparatus transmits a collision confirmation message to the mobile station apparatus having been able to receive the M3, i.e., the message of the upper layers (message 4: M4).
Next, a Non-contention based Random Access procedure will be described simply. First, the base station apparatus informs the mobile station apparatus of a preamble number (or a sequence number) and a random access channel number to be used (message 0: N1). The mobile station apparatus transmits to the specified random access channel RACH a random access preamble of the specified preamble number (message 1: N2). Subsequently, the base station apparatus having received the random access preamble transmits a response to the random access preamble (random access response) to the mobile station apparatus (Message 2: N3).
The Contention based Random Access procedure will be described specifically. First, the mobile station apparatus selects a sequence group based on a downlink path loss or a size of the message 3. Next, one CAZAC sequence is randomly selected from the selected sequence group, and a random access preamble is generated based on the selected CAZAC sequence. Subsequently, the random access preamble is transmitted with the random access channel RACH (message 1 (M1)).
If the base station apparatus detects the random access preamble from the mobile station apparatus, it calculates an amount of transmission timing gap between the mobile station apparatus and the base station apparatus in accordance with the random access preamble. Subsequently, the base station apparatus performs scheduling (specifying a position of an uplink wireless resource, a transmission format (message size), etc.) in order to transmit an L2/L3 (Layer2/Layer3) message, and allocates Temporary C-RNTI (Cell-Radio Network Temporary Identity, i.e., mobile station apparatus identification information). Subsequently, the base station apparatus arranges in the physical downlink control channel PDCCH RA-RNTI (Random Access-Radio Network Temporary Identity) indicating the response to the mobile station apparatus that transmitted the random access preamble of the random access channel RACH (random access response). Subsequently, the base station apparatus transmits to the physical downlink shared data channel PDSCH a random access response message including: transmission timing gap information; scheduling information; and the Temporary C-RNTI and a preamble number (sequence number) of the received preamble (Message 2 (M2)). Note that a wireless resource allocated to the mobile station apparatus by the random access response is only for one resource block (one subframe).
If the mobile station apparatus detects that the physical downlink control channel PDCCH has the RA-RNTI, it confirms a content of the random access response message arranged in the physical downlink shared data channel PDSCH. If the preamble number corresponding to the transmitted random access preamble is included in the content as a result of confirmation, the mobile station apparatus extracts message information, corrects a transmission timing gap, and transmits the L2/L3 message including information that identifies the mobile station apparatus, such as C-RNTI (or Temporary C-RNTI) or IMSI (International Mobile Subscriber Identity), using a scheduled wireless resource and a transmission format (Message 3 (M3)). It is to be noted that the mobile station apparatus continues waiting for the random access response message from the base station apparatus for a certain period, and that the mobile station apparatus transmits the random access preamble again if it does not receive the random access response message including the preamble number of the transmitted random access preamble.
If the base station apparatus receives the L2/L3 message from the mobile station apparatus, it transmits to the mobile station apparatus a collision confirmation (contention resolution) message for determining whether or not collision has occurred between the mobile station apparatuses using the C-RNTI (or Temporary C-RNTI) or the IMSI included in the received L2/L3 message (message 4 (M4)). It is to be noted that the mobile station apparatus starts again from transmission of the random access preamble (message 1 (M1)) (for example, refer to Non-Patent Document 2), if it does not detect the random access response message including the preamble number corresponding to the random access preamble transmitted within the certain period, if it failed to transmit the message 3, or if it does not detect identification information of the mobile station apparatus itself in the collision confirmation message within the certain period. It is to be noted that control data for connection is further exchanged between the base station apparatus and the mobile station apparatus after the end of the random access procedure.
A handover procedure in an EUTRA system is shown in FIG. 20. The above-described random access procedure is utilized in the handover procedure. If data communication is performed between the mobile station apparatus and a base station apparatus 1, the mobile station apparatus transmits to the base station apparatus 1 a measurement report created by measuring a received quality of another base station apparatus. The base station apparatus 1 decides whether to execute handover based on the measurement report from the mobile station apparatus, and if it executes the handover, it decides a base station apparatus to which the handover is performed. Subsequently, the base station apparatus 1 transmits an HO Request message to a base station apparatus (base station apparatus 2) to which the handover is performed.
When the base station apparatus 2 receives the HO Request, it decides whether to permit the handover, and if it permits the handover, it transmits an HO Request Ack message to the base station apparatus 1. Information on the base station apparatus 2, information for performing random access, etc. are included in the HO Request Ack message. If the base station apparatus 1 receives the HO Request Ack message, it transmits to the mobile station apparatus an HO Command message including information included in the HO Request Ack.
If the mobile station apparatus receives the HO Command message, in order to execute the handover, it first performs synchronous processing for synchronizing with a downlink of the base station apparatus 2, and then, it performs random access with respect to the base station apparatus 2 based on the information on the random access included in the HO Command message. At this time, if a random access preamble number and a random access channel number to be used are included in the HO Command, the Non-contention based Random Access procedure is performed, and if not included, the Contention based Random Access procedure is executed.
The mobile station apparatus receives a random access response after transmitting the random access preamble, transmits a handover completion message to the base station apparatus 2 based on uplink wireless resource allocation information included in the random access response, and then the handover is completed. It is to be noted that a timer used in the handover is included in the HO Command, and that the mobile station apparatus repeats random access preamble transmission processing and random access response reception processing until the timer expires if it cannot receive the random access response from the base station apparatus 2. If the mobile station apparatus cannot receive the random access response even though the timer expires, it starts with retrieval of the base station apparatus deciding that the handover has failed.
In addition, discussion on Advanced-EUTRA, which is further evolved EUTRA, has also started in 3GPP. In Advanced-EUTRA, it is assumed that a band up to a 100 MHz bandwidth is used in the uplink and the downlink, respectively, and that communication is performed at a transmission rate not less than up to 1 Gbps in the downlink and up to 500 Mbps in the uplink.
Additionally, in Advanced-EUTRA, it is considered that the 100 MHz band is achieved by binding a plurality of 20 MHz bands of EUTRA so that the mobile station apparatus of EUTRA can also house the 100 MHz band (for example, refer to Non-Patent Document 3). It is to be noted that one 20 MHz band of EUTRA is called a component carrier (CC) in Advanced-EUTRA. FIGS. 21 and 22 are illustrations showing component carriers.
In addition, in Advanced-EUTRA, it is also considered that cooperative transmission, in which the same signal is transmitted at the same time and at the same frequency between adjacent base station apparatuses, is performed in order to increase a communication efficiency of the mobile station apparatus in a cell edge located far from the base station apparatus, and that a throughput of the mobile station apparatus near the cell edge is increased to thereby improve a throughput of the whole system.